This invention relates to a cartridge-based data storage system in which a flexible magnetic disk is disposed within a cartridge shell. More particularly, the invention relates to a shutter for a disk cartridge.
Flexible-media disk cartridges with rotary shutters have been suggested for a decade or more. For example, a cartridge having a rotary shutter is disclosed in U.S. Pat. No. Re. 32,876 (Wakabayashi et al.). The Wakabayashi patent discloses a disk cassette that contains a flexible magnetic disk for storing information. The disk cassette comprises a flexible disk attached to a hub. The disk and hub assembly are sandwiched between upper and lower covers. Disk-access openings are formed in the upper and lower covers to provide access by the read/write heads of a disk drive. The Wakabayashi shutter rotates on the interior of the cartridge and comprises a metal sheet that slides over and thereby selectively covers the disk-access openings. This design represents an alternative to the more common sliding shutter found in 1.44 megabyte floppy disks, and may be preferable for a flexible-media disk cartridge in which the disk-access opening is relatively small.
A rotary shutter for a disk-access opening that is large relative to the cartridge size has more recently been disclosed. For example, U.S. Pat. No. 5,636,095 (McGrath et al.) describes a rotary shutter that covers a significant percentage of the medium within the cartridge. The McGrath cartridge comprises a hard-disk medium that is rotatably disposed within an outer shell, and a shutter that rotates within the outer shell to selectively expose and cover the medium.
Typically, the shutter and the outer shell of disk cartridges are manufactured from metal or plastic materials, and are placed in direct contact with each other. This contact maintains proper alignment between the two components while the shutter is in the open or closed positions, and while the shutter moves between these positions. Proper alignment is necessary to prevent the shutter from jamming, and to prevent the shutter and the magnetic medium from coming into contact. Such contact can lead to damage of the medium and loss of data stored on the medium.
Direct contact between the outer shell and the shutter causes wear on the contact surfaces both components. This wear eventually produces misalignment and jamming of the shutter, which can damage the magnetic medium and preclude further use of the disk cartridge. Such contact and wear also generates contaminants which can harm the disk cartridge as well as the disk drive in which the cartridge is installed.
Thus, a need exists for an improved disk cartridge in which the sliding friction between the contact surfaces of the shell and the shutter is reduced, while sufficient contact is maintained to keep the shell and the shutter in proper alignment.